Fate Tracing Reveals the Pericyte and Not Epithelial Origin of Myofibroblasts in Kidney Fibrosis

Renal Division, Department of Medicine, Brigham & Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
American Journal Of Pathology (Impact Factor: 4.59). 12/2009; 176(1):85-97. DOI: 10.2353/ajpath.2010.090517
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Understanding the origin of myofibroblasts in kidney is of great interest because these cells are responsible for scar formation in fibrotic kidney disease. Recent studies suggest epithelial cells are an important source of myofibroblasts through a process described as the epithelial-to-mesenchymal transition; however, confirmatory studies in vivo are lacking. To quantitatively assess the contribution of renal epithelial cells to myofibroblasts, we used Cre/Lox techniques to genetically label and fate map renal epithelia in models of kidney fibrosis. Genetically labeled primary proximal epithelial cells cultured in vitro from these mice readily induce markers of myofibroblasts after transforming growth factor beta(1) treatment. However, using either red fluorescent protein or beta-galactosidase as fate markers, we found no evidence that epithelial cells migrate outside of the tubular basement membrane and differentiate into interstitial myofibroblasts in vivo. Thus, although renal epithelial cells can acquire mesenchymal markers in vitro, they do not directly contribute to interstitial myofibroblast cells in vivo. Lineage analysis shows that during nephrogenesis, FoxD1-positive((+)) mesenchymal cells give rise to adult CD73(+), platelet derived growth factor receptor beta(+), smooth muscle actin-negative interstitial pericytes, and these FoxD1-derivative interstitial cells expand and differentiate into smooth muscle actin(+) myofibroblasts during fibrosis, accounting for a large majority of myofibroblasts. These data indicate that therapeutic strategies directly targeting pericyte differentiation in vivo may productively impact fibrotic kidney disease.

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Available from: Ben Humphreys, May 16, 2014
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    • "To preserve β-galactosidase activity, liver tissue was fixed in PLP (4% paraformaldehyde (PFA), 75 mM l-lysine, 10 mM sodium periodate) for 2 hours at 4°C, cryopreserved in 18% sucrose, frozen in optimum cutting temperature compound, and 5-µm cryosections were prepared for X-gal labeling or immunofluorescence (IF). LacZ activity was measured using a standard 5-bromo-4-chloro-3-indolyl-β-d-galactoside (X-gal) staining protocol [46] for 16 hours at 37°C. After washing, sections were post-fixed in 1% PFA for 5 minutes and immunolabeled for additional histologic analysis (see below). "
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    PLoS ONE 10/2014; 9(10):e108505. DOI:10.1371/journal.pone.0108505 · 3.23 Impact Factor
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    • "No therapy has been established to prevent renal fibrosis. Since many different kinds of cell, such as immune cells, vascular endothelial cells, tubular epithelial cells and fibroblasts, have been considered to contribute to the development of renal fibrosis, the investigation of therapeutic approaches, including the exploration of target genes, for the inhibition of renal fibrosis in vivo is crucially important to improve the prognosis of all chronic kidney diseases56789101112. "
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    Scientific Reports 09/2014; 4:6424. DOI:10.1038/srep06424 · 5.58 Impact Factor
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    • "The sources of renal myofibroblasts are local resident fibroblasts that arise from proliferation (50%), and nonproliferating myofibroblasts derived from bone marrow (35%) [25]. It has been proposed that the remaining progenitor population is derived from circulating fibrocytes, local pericytes, and resident epithelial cells, although this remains to be fully characterized [26], [27]. α-SMA expression induces fibroblasts into myofibroblasts [28]. "
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